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New Test to Prevent Long Bone Deformity

SCOTLAND - A new test for measuring manganese in cattle is to help reduce long bone deformity in their calves.

Scotland's Rural College has launched a new test for long bone deformity or congenital chondrodystrophy in calves has been linked to manganese deficiency in the mother during pregnancy.

It is thought to occur when the cow’s requirement of manganese has been provided almost entirely by ensiled forage both grass and whole crop.

It is believed the manganese remains “locked up” in the ration through the presence of some as yet unknown compound within the silage, preventing the cow from absorbing it fully.

Until now it has been difficult to measure the blood levels of manganese. Instead, farmers rely on reducing the amount of silage in a cow’s feed ration, which can be wholly or partially successful in most situations. Where it is not possible to alter the proportion of silage, manganese supplementation can be used. Over the past year, mineral supplements with increased amounts of manganese have become available.

SRUC Veterinary Services (part of SAC Consulting, a Division of SRUC) has now established an assay (test) to measure the concentration of manganese in the blood of the cows and provide a tool to monitor manganese levels in herds where there is a high risk of calves being born with long bone deformity.

SRUC Veterinary Manager George Caldow said: “We recommend that once cows have been on the silage ration for more than one week they should be blood sampled. At least six cows should be bled.

Where low concentrations of manganese are found then the manganese enriched mineral supplement can be added to the ration. Follow up sampling can then be carried out to show the effect that the supplementation has had on the blood manganese concentration.

“It is also important to recognise that certain mycotoxins can have impact on the normal growth of bones in the developing calf during pregnancy and cause a similar deformity. Therefore visibly spoiled forage should not be fed to pregnant cows to minimise this risk.”